In storage media systems, it is important to maintain the fly height of the head within a prescribed region. If the fly height is too great, the signals transmitted and read by the head will be too weak for accurate data storage and retrieval. If the fly height is too small, the head can physically contact the medium, causing physical damage to the medium and loss of the data stored on the medium.
Methods for detecting fly height generally employ a known pattern written on the storage medium. In response to the pattern, the head produces one or more pulses. One conventional method to detect fly height measures the peak amplitude of the pulse. Another conventional method is to measure the duration of the pulse, for example at its half-amplitude point. Still another method involves measuring the area under the pulse. These method are unreliable because the amplitude of the pulse, and the area under the pulse, are affected unpredictably by factors such as the gain of the storage system.